Speed up Ability definition on person by not using scope.

I'm not sure why using the 'undeleted' scope was so slow here. It seems
to add about 1-2 seconds every time it is called -- perhaps it is
querying *all* undeleted Persons in order to determine if any of them
match the conditions in the third parameter?
Add authorization for Messages.
Refactor Ability class.
Add authorization for PrayerRequests.
Fix copy pasta test labels.
Add authorization for Albums in a group the user manages.
Add authorization for Pictures.
Add authorization for Notes and Comments.
Allow numbers in page slug.
Add authorization for remaining models. Disallow frozen accounts.
Remove attachments from pages.
Add fixme note to people controller.
Add AlbumsController test for existing code, fix bug with double-render.